This invention relates to an antiplaque gel dentifrice which is visually clear.
Dentifrices which are visually clear are appealling to consumers. Numerous visually clear products have been sold commercially as gel dentfrices.
Clarity however, can reveal other problems. Thus, when a liquid organic gel dentifrice component acts as a solvent to facilitate dissolving of a substantially water-insoluble component, conditions can arise in which a portion of the organic solvent separates into crystals which detract aesthetically from the clear appearance of the gel dentifrice, although without negatively impacting on hygienic effectiveness.
In recent years, substantially water-insoluble non-cationic antibacterial agents have been found to be effective antiplaque agents in oral compositions, particularly when used in combination with an antibacterial-enhancing agent (AEA) which improves delivery to and retention on oral tooth and gum surfaces of the antibacterial agent. As described in U.S. Pat. Nos. 5,354,550 and 5,253,313 of Collins et al, it has been possible to prepare clear gel dentfrices containing such antibacterial agent and polycarboxylate as AEA.
The prior art considerations for attaining clarity ranging from haze or translucency to high transparency have, in general, been based upon employing a dentifrice polishing agent having a refractive index of about 1.41 to about 1.47, properly balancing with water (refractive index 1.333) and humectant, most usually glycerine (refractive index 1.473) and sorbitol (refractive index 1.457, as 70% aqueous solution). Since the refractive index of grades of siliceous polishing agents, the most frequently used type of polishing agents in gel dentifrices, is usually about 1.41 to about 1.47, although water ranges in the dentifrices such as up to about 30% by weight have been disclosed, the amount of water is generally kept low, say about 3% by weight, when transparency and not merely turbid translucency is desired.
The need to dissolve small amounts of normally insoluble materials such as noncationic antibacterial agents also can present a challenge to achieving clarity. Flavor oil and surfactant are generally used to dissolve such materials.
As indicated above, clarity can be attained in gel dentifrices containing substantially water-insoluble noncationic antibacterial agents as is described in U.S. Pat. Nos. 5,354,550 and 5,253,213 and reasonable clarity may be obtained when polycarboxylate is present even somewhat outside of the parameters of these patents. However, when the gel dentfrice is visually clear (that is transparent or translucent) and contains a substantially water-insoluble noncationic antibacterial agent, such as triclosan, and sodium lauryl sulfate, the most common dentifrice surfactant, as an organic solvent to facilitate dissolving the antibacterial agent, under cool temperature conditions (below about 20.degree. C.), crystals can separate from the surfactant and substantially diminish clarity of the gel dentifrice.
In the present invention, alternative surfactant systems reduced crystal formation while still permitting substantial retention of gel dentifrice clarity. These systems are particularly Tergitol.RTM. sulfate as surfactant or mixtures of sodium lauryl sulfate with Tergitol.RTM. sulfates or with taurates.
The art has previously disclosed dentifrices containing substantially water-insoluble noncationic antibacterial agent with alternative surfactant systems but without achieving the present invention. Indeed, the crystal formation problem solved in the present invention appears not to have even been recognized in the prior art.
In U.S. Pat. No. 5,135,738 to Gaffar et al, triclosan dentifrices are disclosed which may be manufactured with a mixture of sodium lauryl sulfate and sodium methyl cocoyl taurate. However, the only dentifrices which are specifically prepared which contain silica polishing agent are not clear (for instance, due to the presence of titanium dioxide, an opacifying agent.
In U.S. Pat. No. 5,356,615 to Gaffar, a mixed surfactant system of Tauranol.RTM. WS and sodium lauryl sulfate is disclosed for triclosan mouthwash. Such a system is not indicated for disclosed triclosan toothpaste with silica polishing agent, which in any event, in the manner in which it is exemplified, is not visually clear.
In Japanese Public Patent Disclosure H4-139117 to Lion Corporation a liquid dentifrice is disclosed in Example 23 which contains sodium lauryl sulfate and sodium N-lauryl-N-methyl taurate. The liquid dentfrice contains 10% zirconium silicate (which has a refractive index of about 1.9 to 2.0) and cannot be clear.
In European Patent Publication 161898 to Unilever PLC, dentifrice with silica xerogel polishing agent and triclosan is disclosed which contains sodium lauryl sulfate and sodium dodecylbenzene sulfonate. However, in clear gel dentifrices, this surfactant system would not avoid the formation of sodium lauryl sulfate crystals when the dentifrice is subject to cool temperatures.
In chapter 11 (Molecular Interactions and Synergism in Mixtures of Two Surfactants) Rosen, M. J., of "Surfactants and Interfacial Phenomena", 2nd Edition, 1989, John Wiley and Sons, Inc., New York, (pages 393-419), the author sets forth guidelines for predicting synergistic effects with particular surfactant mixtures. These guidelines, however, are applicable to water systems rather than to complete formulations such as dentifrices. Further, it is not appropriate to apply such guidelines to a problem which has not previously been recognized, such as the formation of visible sodium lauryl sulfate crystals in clear gel dentifrices subject to cool temperature conditions.
It is an advantage of this invention that stable visual clarity is attained in a gel dentifrice containing substantially water-insoluble noncationic antibacterial agent and surfactant solvent therefore, such that visible crystals are not observed as a result of surfactant separation.
Other advantages of the invention will be apparent from consideration of the following specification.
In accordance with certain of its aspects, this invention relates to a visually clear gel dentifrice comprising about 5-50% by weight of a dentally acceptable dentifrice polishing agent having a refractive index in the range of about 1.41 to about 1.47, about 0.1-10% by weight of a gelling agent to provide a gel consistency to said dentifrice, at least about 20% by weight of a liquid aqueous-humectant vehicle having a refractive index within about 0.02 refractive index units of said polishing agent, about 0.01-5% by weight of a substantially water-insoluble noncationic antibacterial agent, which is partially dissolved in about 0.1-3% by weight of flavoring oil, and about 0.5-5% by weight of surfactant which facilitates dissolving of said antibacterial agent in said gel dentfrice, the improvement characterized in that said surfactant is
(a) a polyoxyethylene alcohol sulfate having the formula EQU R--(O CH.sub.2 CH.sub.2).sub.n.sup.- OSO.sub.3.sup.- X.sup.+, PA0 (b) a weight mixture of at least about 1:3 of said polyoxyethylene alcohol sulfate with alkali metal lauryl sulfate or PA0 (c) a weight mixture of about 3:1 to about 1:3 of alkali metal lauryl sulfate with an N-acyl-N-alkyltaurate having the formula: ##STR1## wherein R' is an alkyl group with a C.sub.10-24 linear hydrocarbon chain length, R" is a C.sub.1-4 n-alkyl group and X is alkali metal. As used herein, alkali metal includes the Group 1A metals, especially sodium and potassium, and functionally equivalent ammonium. PA0 2',4,4'-trichloro-2-hydroxy-diphenyl ether (Triclosan) PA0 2,2'-dihydroxy-5,5'-dibromo-diphenyl ether. PA0 4',5-dibromosallcylanilide PA0 3,4',5-trichlorosalicylanilide PA0 3,4',5-tribromosalicylanilide PA0 2,3,3',5-tetrachlorosalicylanilide PA0 3,3,3',5-tetrachlorosalicylanilide PA0 3,5-dibromo-3'-trifluoromethyl salicylanilide PA0 5-n-octanoyl-3'-trifluoromethyl salicylanilide PA0 3,5-dibromo-4'-trifluoromethyl salicylanilide PA0 3,5-dibromo-3'-trifluoro methyl salicylanilide (Fluorophene) PA0 Methyl-p-Hydroxybenzoic Ester PA0 Ethyl-p-Hydroxybenzoic Ester PA0 Propyl-p-Hydroxybenzoic Ester PA0 Butyl-p-Hydroxybenzoic Ester PA0 Famesol PA0 Nerolidol PA0 Bisabolol PA0 Santalol PA0 3,4,4'-trichlorocarbanilide PA0 3-triffuoromethyl-4,4'-dichlorocarbanilide PA0 3,3,4'-trichlorocarbanilide PA0 Phenol PA0 2-Methyl-Phenol PA0 3-Methyl-Phenol PA0 4-Methyl-Phenol PA0 4-Ethyl-Phenol PA0 2,4-Dimethyl-Phenol PA0 2,5-Dimethyl-Phenol PA0 3,4-Dimethyl-Phenol PA0 2,6-Dimethyl-Phenol PA0 4-n-Propyl-Phenol PA0 4-n-Butyl-Phenol PA0 4-n-Amyl-Phenol PA0 4-tert-Amyl-Phenol PA0 4-n-Hexyl-Phenol PA0 4-n-Heptyl-Phenol PA0 2-Methoxy-4-(2-Propenyl)-Phenol (Eugenol) PA0 2-Isopropyl-5-Methyl-Phenol (Thymol) PA0 Methyl-p-Chlorophenol PA0 Ethyl-p-Chlorphenol PA0 n-Propyl-p-Chlorophenol PA0 n-Butyl-p-Chlorophenol PA0 n-Amyl-p-Chlorophenol PA0 sec-Amyl-p-Chlorophenol PA0 n-Hexyl-p-Chlorophenol PA0 Cyclohexyl-p-Chlorophenol PA0 n-Heptyl-p-Chlorophenol PA0 n-Octyl-p-Chlorophenol PA0 o-Chlorophenol PA0 Methyl-o-Chlorophenol PA0 Ethyl-o-Chlorophenol PA0 n-Propyl-o-Chlorophenol PA0 n-Butyl-o-Chlorophenol PA0 n-Amyl-o-Chlorophenol PA0 tert-Amyl-o-Chlorophenol PA0 n-Hexyl-o-chlorophenol PA0 n-Heptyl-o-Chloropenol PA0 p-Chlorophenol PA0 o-Benzyl-p-Chlorophenol PA0 o-Benzyl-m-methyl-p-Chlorophenol PA0 o-Benzyl-m, m-dimethyl-p-Chlorophenol PA0 o-Phenylethyl-p-Chlorophenol PA0 o-Phenylethyl-m-methyl-p-Chlorophenol PA0 3-Methyl-p-Chlorophenol PA0 3,5-Dimethyl-p-Chlorophenol PA0 6-Ethyl-3-methyl-p-Chlorophenol PA0 6-n-Propyl-3-methyl-p-Chlorophenol PA0 6-iso-propyl-3-methyl-p-Chlorophenol PA0 2-Ethyl-3,5-dimethyl-p-Chlorophenol PA0 6-sec Butyl-3-methyl-p-Chlorophenol PA0 2-iso-Propyl-3,5-dimethyl-p-Chlorophenol PA0 6-Diethylmethyl-3-methyl-p-Chlorophenol PA0 6-iso-Propyl-2-ethyl-3-methyl-p-Chlorophenol PA0 2-sec-Amyl-3,5-dimethyl-p-Chlorophenol PA0 2-Diethylmethyl-3,5-dimethyl-p-Chlorophenol PA0 6-sec-Octyl-3-methyl-p-Chlorophenol PA0 p-Bromophenol PA0 Methyl-p-Bromophenol PA0 Ethyl-p-Bromophenol PA0 n-Propyl-p-Bromophenol PA0 n-Butyl-p-Bromophenol PA0 n-Amyl-p-Bromophenol PA0 sec-Amyl-p-Bromophenol PA0 n-Hexyl-p-Bromophenol PA0 cyclohexyl-p-Bromophenol PA0 o-Bromophenol PA0 tert-Amyl-o-Bromophenol PA0 n-Hexyl-o-Bromophenol PA0 n-Propyl-m,m-Dimethyl-o-Bromophenol PA0 2-Phenyl Phenol PA0 4-Chloro-2-methyl phenol PA0 4-chloro-3-methyl phenol PA0 4-chloro-3,5-dimethyl phenol PA0 2,4-dichloro-3,5-dimethyl phenol PA0 3,4,5,6-tetrabromo-2-methylphenol PA0 5-methyl-2-pentylphenol PA0 4-isopropyl-3-methylphenol PA0 5-chloro-2-hydroxydiphenyl-3methyl phenol PA0 Resorcinol PA0 Methyl-Resorcinol PA0 Ethyl-Resorcinol PA0 n-Propyl-Resorcinol PA0 n-Butyl-Resorcinol PA0 n-Amyl-Resorcinol PA0 n-Hexyl-Resorcinol PA0 n-Heptyl-Resorcinol PA0 n-Octyl-Resorcinol PA0 n-Nonyl-Resorcinol PA0 Phenyl-Resorcinol PA0 Benzyl-Resorcinol PA0 Phenylethyl-Resorcinol PA0 Phenylpropyl-Resorcinol PA0 p-Chlorobenzyl-Resorcinol PA0 5-Chloro-2,4-Dihydroxydiphenyl Methane PA0 4'-Chloro-2,4-Dihydroxydiphenyl Methane PA0 5-Bromo-2,4-Dihydroxydiphenyl Methane PA0 4'-Bromo-2,4-Dihydroxydiphenyl Methane PA0 Bisphenol A (2,2-bis(4-hydroxyphenyl) propane) PA0 2,2'-methylene bis(4-chlorophenol) PA0 2,2'-methylene bis(3,4,6-trichlorophenol) (hexachlorophene) PA0 2,2 '-methylene bis(4-chloro-6-bromophenol) PA0 bis (2-hydroxy-3,5-dichlorophenyl) sulfide PA0 bis (2-hydroxy-5-chlorobenzyl) sulfide
wherein R is an alkyl group with a C.sub.10-18 hydrocarbon chain length, n is an integer of 1 to about 4 and X is alkali metal or
Typical examples of substantially water insoluble noncationic antibacterial agents which are particularly desirable for their antiplaque effectiveness, safety and formulation are:
Halogenated Diphenyl Ethers
Halogenareal Salicylanilides
Benzoic Esters
Sesquiterpene Alcohols
Halogenated Carbanilides
Phenolic Compounds (including phenol and its homologs, mono- and poly-alkyl and aromatic halo (e.g. F, Cl, Br, I)-phenols, resorcinol and catechol and their derivatives and bisphenolic compounds). Such compounds include inter alia:
Phenol and its Homologs
Mono- and Poly-Alkyl and Aralkyl Halophenols
Resorcinol and Its Derivatives
Bisphenolic Compounds
The noncationic antibacterial agent is present in the gel dentifrice composition of the present invention in an effective antiplaque amount typically about 0.01-5% by weight, preferably about 0.03-1% and most preferably about 0.3-0.6%. The antibacterial agent is substantially water-insoluble, meaning that its solubility is less than about 1%.
The preferred halogenated diphenyl ether is triclosan. The preferred phenolic compounds are phenol, thymol, eugenol, and 2,2'methylene bis(4-chloro-6-bromophenol). The preferred sesquiterpene alcohols are nerolidol and bisabolol.
The dentally acceptable dentifrice polishing agent has a refractive index in the range of about 1.41 to about 1.47. Thus, it may be a finely divided synthetic amorphous silica having an average refractive index of from about 1.410 to 1.440 as has been described for translucent dental creams in U.S. Pat. Nos. 3,939,262 and 4,007,260, each to Kim or an alkali metal phosphate salt having a refractive index between 1.435 and about 1.465 as has been described in U.S. Pat. No. 3,927,202 to Harvey et al. The alkali metal phosphate polishing agents described therein are potassium metaphosphate, which is water-insoluble and water-soluble sodium pyrophosphate dodecahydrate, dibasic sodium orthophosphate dihydrate, dibasic sodium orthophosphate heptahydrate and tribasic sodium orthophospahte dodecahydrate.
Preferably the polishing agent is a siliceous material such as a hydrous silica gel, a silica xerogel or a complex amorphous alkali metal aluminosilicate or zirconosilicate having a refractive index of about 1.44 to 1.48 or a precipitated silica having a refractive index of about 1.41 to 1.45. Colloidal silica materials include those sold under the trademark SYLOID such as those which have been sold as Syloid 72 and Syloid 74, Precipitated silicas include those sold under the trademark ZEODENT by J. M. Huber Corporation such as Zeodent 113 and Zeodent 115 and Zeodent 119.
The complex aluminosilicate salt appears to contain interbonded silica and alumina having Al-O-Si bonds as described by Tamele, "Chemical of the Surface and Activity of Alumina-Silica Craking Catalyst", Discussions of the Faraday Society, No. 8, Pages 270-279 (1950) and particularly at Page 273, FIG. 1, Curve 3 wherein the interaction between silica and aluminum ions is potentiometrically detected. Further literature describing this type of complex includes Milliken et al., "The Chemical Characteristics and Structure of Craking Catalysts", Discussions of the Faraday Society, No. 8, Pages 279-290 (1950) and particularly the sentence bridging Pages 284-285. These complexes clearly differ from silica gel as is described by Plank et al., "Differences Between Silica and Silica-Alumina Gels I. Factors Affecting the Porous Structure of These Gels," Journal of Colloid Science, 2. Pages 399-412 (1947) and Plank, "Differences Between Silica and Silica-Alumina Gels II. A Proposed Mechanism for the Gelation and Syneresis of These Gels." Journal of Colloid Science 2, Pages 423-427, (1947) in which formation of the Al-O-Si bond is described at Pages 419-422.
The liquid vehicle, when mixed with gelling agent, forms a gel mass of consistency which desirably can be extruded from a collapsible opaque or clear plastic, aluminum or lined tube or other squeeze, pump or pressurized dispenser. The liquid vehicle comprises at least about 20% by weight of the gel dentifrice (e.g. about 20-94.39%) and is typically composed of water and humectant such as glycerine, sorbitol, propylene glycol and the like. Sorbitol, glycerine and mixtures thereof are preferred humectants due to their generally excellent humectant properties and their refractive indices which permit formulation of the liquid vehicle with a refractive index within about 0.02 units of the refractive index of the polishing agent. Thus sorbitol (commercially available in 70% aqueous solution), has a refractive index of 1.457 and glycerine (99.5% aqueous solution) has a refractive index of 1.473. The refractive index of water is 1.33.
A gel vehicle containing about 25-28% water (apart from water provided as humectant solvent), about 10-12% of 99.5% glycerine solution and about 30-35% of 70% sorbitol solution can readily provide a refractive index of about 1.43 to 1.46 and permit formation of a clear gel dentifrice in which the refractive index of the polishing agent is about 1.41 to 1.47 and within 0.02 of the refractive index of the liquid vehicle.
Should the gel dentifrice contain a polycarboxylate as an antibacterial-enhancing agent (AEA) to enhance delivery and retention of the substantially water-insoluble noncationic antibacterial agent to oral tooth and gum surfaces, the relative amounts of liquid vehicle water and humectant components can be adjusted in order to provide clarity to a dentifrice containing a polishing agent having a refractive index of about 1.41 to 1.47, for instance as described in U.S. Pat. No. 5,252,313, to Collins et al, the disclosure of which is incorporated herein by reference.
When present to enhance delivery and retention of the antibacterial agent water-swellable synthetic artionic polymeric polycarboxylate typically has a molecular weight of about 1,000 to about 1,000,000 or more, preferably about 30,000 to about 500,000.
The water-swellable synthetic anionic polymeric polycarboxylates are preferably employed as partially or completely neutralized water swellable alkali metal (or ammonium) salts but may also be used in their free acids. Preferably they are 4:1 to 1:4 copolymers of maleic anhydride or maleic acid with another polymerizable ethylenically unsaturated monomer, which is very preferably methyl vinyl ether, and the copolymer will have a molecular weight in the range of about 5,000-2,000,000, preferably about 30,000-1,500,000, more preferably about 50,000-1,100,000 and most preferably about 50,000-100,000, as determined by vapor pressure osmometry. A preferred range of molecular weights, by gel permeation chromatography against a polyethylene glycol standard, is about 500,000 -1,500,000, more preferably about 1,000,000-1,100,000, e.g., about 1,090,000. Useful such polycarboxylates include Luviform.RTM. FA-139 of BASF and GAF's Cantfez.RTM. AN 169, AN 139, AN 119 and S-97, pharmaceutical grade. The Cantfez polycarboxylates have been reported by their manufacturer to be of molecular weights of about 750,000, 500,000, 250,000 and 70,000, respectively, but by gel permeation chromatography determinations (against a polyethylene glycol standard) the S-97, pharmaceutical grade, is of a molecular weight in the range of about 1,000,000 -1,100,000 (the lower molecular weight of 70,000, was determined by vapor pressure osmometry). The polymers such as the Luviform and Cantfez polymers may be incorporated into the gel dentifrices in solid form or in aqueous solution. When aqueous solution is employed, the aqueous solvent forms a portion of the total water in the liquid vehicle. The mentioned Luviform and Cantfez copolymers are all linear copolymers but crosslinked polymers, such as those sold under the trademark Carbopol, of BF Goodrich, e.g., Carbopol 934, 940 and 941, may be substituted, at least in part (e.g., about 1% or more ). Since aqueous solutions of Cantfez copolymer are typically available as 13% solutions and aqueous solutions of Luviform copolymer can be typically available as about 25-35%, say 26% solutions, less water is introduced into the clear gel dentifrice with Luviform solution than with Gantrez solution, making it somewhat easier to maintain clarity under Luviform solution than with Cantfez solution.
Other water-swellable polymeric polycarboxylates include the 1:1 copolymers of maleic anhydride with ethyl acrylate, hydroxyethyl methacrylate, N-vinyl-2-pyrollidone, or ethylene, the later being available for example as Monsanto EMA No. 1103, M. W. 10,000 and EMA Grade 61, and 1:1 copolymers of acrylic acid with methyl or hydroxyethyl methacrylate, methyl or ethyl acrylic acid with methyl or hydroxyethyl methacrylate, methyl or ethyl acrylate, isobutyl vinyl ether or N-vinyl-2-pyrrolidone.
Additional water-swellable polymeric polycarboxylates include copolymers of maleic anhydride with styrene, isobutylene or ethyl vinyl ether, polyacrylic, polyitaconic and polymaleic acids, and sulfoacrylic oligomers of M. W. as low as 1,000, available as Uniroyal ND-2.
Suitable, also, generally are polymerized olefinically or ethylenically unsaturated carboxylic acid containing an activated carbon-to-carbon olefinic double bond and at least one carboxyl group, that is, an acid containing an olefinic double bond which readily functions in polymerization because of its presence in the monomer molecule either in the alpha-beta position with respect to a carboxyl group or as part of a terminal methylene grouping. Illustrative of such acids are acrylic, methacrylic, ethacrylic, alpha-chloroacrylic, crotonic, beta-acryloxy propionic, sorbic, alpha-chlorsorbic, cinnamic, beta-styrilacrylic, muconic, itaconic, citraconic, mesaconic, glutaconic, aconitic, alpha-phenylacrylic, 2-benzyl acrylic, 2-cyclohexylacrylic, angelic, umbellic, fumaric, maleic acids and anhydrides. Other different olefinic monomers copolymerizable with such carboxylic monomers include vinylacetate, vinyl chloride, dimethyl mateate and the like. Copolymers contain sufficient carboxylic salt groups for water-solubility, typically as alkali metal (especially sodium or potassium), including ammonium.
In addition to the described possible presence of polycarboxylates as antibacterial-enhancing agents (AEA's), other AEA's, for instance as described in U.S. Pat. No. 5,032,386 to Gaffar et al, such as polyphosphates, polyphosphinates and polysulfonate polymers may be used. The disclosure of U.S. Pat. No. 5,032,386 is incorporated herein by reference. The AEA's are non-toxic and can be present in amount of about 0.05-4% by weight, preferably about 0.1-3% more preferably about 0.5-2.5%.
Gel dentrifices have their gel consistency provided by a natural or synthetic binder, thickener or gelling agent in proportions of about 0.1 to about 10% by weight, preferably about 0.5 to about 5%.
Suitable thickeners include Irish moss, iota carrageenan, gum tragacanth starch, polyvinylpyrrolidone, hydroxyethylpropylcellulose, hydroxybutyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose (e.g. available as Natrosol), sodium carboxymethyl cellulose, and colloidal silica such as finely ground Syloid (e.g. 244). Sodium carboxymethyl cellulose is preferred, even including grades having a viscosity above 20 cps measured as 1% aqueous solution at 25.degree. C., e.g. CMC-7MF and CMC-7MFX available from Hercules.
It will be understood that, as is conventional, the gel dentifrice preparations are to be sold or otherwise distributed in suitably labeled collapsible tubes, typically aluminum, lined lead or opaque or clear plastic, or other squeeze, pump or pressurized dispenser for metering out the contents, having a label describing it in substance, as a gel dentifrice or toothpaste.
Organic surface-active agents are used in the compositions of the present invention to achieve increased prophylactic action, assist in achieving thorough and complete dispersion of the dentifrice throughout the oral cavity, and render the instant compositions more cosmetically acceptable. The particular organic surfactant employed in the present invention is anionic and is present in amount of about 0.5-5% by weight, preferably about 0.8-3.5%. While it imparts to the composition detersive and foaming properties, it also exercises solvent properties for the substantially water-insoluble non-cationic antibacterial agent and provides visually clear gel dentifrices containing such antibacterial agents with reduced tendency to form unsightly crystals when the gel dentifrice is subject to cool temperatures, below about 20.degree. C., such as between about 5.degree. to 15.degree. C.
The surfactant may desirably be the anionic sulfate of the nonionic polyoxyoxyeghylenated alcohol available under the name Tergitol.RTM. from Union Carbide Company. A preferred sulfate Terigol, available as Terigol 24.L-2NMW Sulfate, is represented by the formula: EQU R--(OCH.sub.2 CH.sub.2).sub.n.sup.- OSO.sub.3.sup.- X.sub.a.sup.+,
wherein X is Na, n is an average of 2 and R has a linear hydrocarbon length is 12-14. However, more generally X is alkali metal such as sodium or potassium (and including functionally equivalent ammonium), n is an integer of 1 to about 4, preferably 2, and R is an alkyl group with linear hydrocarbon chain length of C.sub.10-18, preferably C.sub.12-16.
The sulfated surfactant having the general formula represented above can be used in amount of about 0.5-5% by weight, preferably about 0.8-2.5%, most preferably about 1.2-2.5%, as the sole surfactant or in at least about 1:3 mixture with alkali metal lauryl sulfate alcohol sulfate salt, typically about 1:3 to about 3:1 and preferably about 1:1 to about 1:3 of the sulfated polyoxyethylenated alcohol to the lauryl sulfate.
The surfactant may also be a mixture of an N-acyl N-alkyltaurate alkali metal salt with alkali metal lauryl sulfate, in a weight ratio of the taurate to the lauryl sulfate of about 3:1 to about 1:3, preferably about 1:1 to about 1:3, most preferably about 1:1.
A preferred taurate is available from Finetex Inc. as Tauranol.RTM.WHSP, represented by the formula: ##STR2## wherein R' is cocoyl, R" is methyl and X is sodium. However, more generally, X can be alkali metal such as sodium or potassium (and including functionally equivalent ammonium), R' is an alkyl group with C.sub.10-18 linear hydrocarbon chain length, preferably C.sub.12-16 and R" is a C.sub.1-4 n-alkyl group, preferably methyl.
Representative taurates include the sodium and potassium salts of N-cocoyl-N-methyltaurate, N-palmitoyl-N-methyltaurate and N-oleyl-N-methyl taurate and their ethyl, n-propyl and n-butyl homologs.
When the surfactant is a mixture of the described salts it is preferred that when one is sodium salt that the other is also; or that each be potassium salts or ammonium salts. Sodium salts are preferred.
Various other materials may be incorporated in the gel dentifrices of this invention such as preservatives, silicones, anticalculus agents, water-soluble dyes, iridescent particles and/or ammoniated material such as urea, diammonium phosphate, and mixtures thereof. These adjuvants, where present, are incorporated in the preparations in amounts which do not substantially adversely affect the properties and characteristics desired.
Any suitable flavoring oil or sweetening material may also be employed. Flavoring oil partially dissolves the noncationic antibacterial agent. Examples of suitable flavoring constituents are flavoring oils, e.g. oil of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, marjoram, cinnamon, lemon, and orange, and methyl salicylate. Suitable sweetening agents include sucrose, d-tryptophan, dihydrochalcones, sodium cyclamate, perillartine, APM (aspartyl phenyl alanine, methyl ester), saccharine and the like. Suitably, flavor and sweetening agents may together comprise from about 0.1% to 5% by weight or more of the preparation, with flavoring oil typically being up to about 3% and sweetening agent typically up to about 2%.
The visually clear gel dentifrices may be prepared in accordance with generally employed preparation techniques, with uniform appearance or with stripes, at least one of which is visually clear. They typically have a pH of about 4.5 to 9, generally about 5.5 to 8, preferably about 6 to 8.